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通过在Activity设计好的界面中输入参数，可以绘制出任意状态的直线、圆形、矩形等

布局文件：

实现效果如下：（后面的界面效果，均是在连接华为Nova4真机下操作的）

【输入以上参数可以绘制出下面的效果图：】

直线：

圆形：

矩形：

public class MainActivity extends AppCompatActivity {
           // 7th    Button rect, circle, line;    TextView x0, y0, x1, y1;    TextView px, py, radius;    TextView lx1, lx2, ly1, ly2;    @Override    protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);        // 7th        setContentView(R.layout.draw_graphic);        init7();    }    public void init7() {
           rect = findViewById(R.id.rect);        circle = findViewById(R.id.circle);        line = findViewById(R.id.line);        // 矩形        x0 = findViewById(R.id.x0);        y0 = findViewById(R.id.y0);        x1 = findViewById(R.id.x1);        y1 = findViewById(R.id.y1);        // 圆形        px = findViewById(R.id.px);        py = findViewById(R.id.py);        radius = findViewById(R.id.radius);        // 直线        lx1 = findViewById(R.id.lx1);        ly1 = findViewById(R.id.ly1);        lx2 = findViewById(R.id.lx2);        ly2 = findViewById(R.id.ly2);    }    // 点击事件处理    // 每次获取控件中的参数之前，一定要排除空数据的情况，这个对于后面进行页面跳转时，    // 传递空数据会报错（空指针异常）对于刚入门的我来讲，是难以发现的，同时也是致命的    public void onClick_7(View view) {
           switch (view.getId()) {
               case R.id.rect:                if (!isEmpty(x0) && !isEmpty(y0)                        && !isEmpty(x1) && !isEmpty(y1)) {
                       String x_0 = x0.getText().toString().trim();                    String x_1 = x1.getText().toString().trim();                    String y_0 = y0.getText().toString().trim();                    String y_1 = y1.getText().toString().trim();                                        // 跳转页面draw_RCL.java                    Intent intent = new Intent(MainActivity.this, draw_RCL.class);                    Bundle bundle = new Bundle();                    // 每次绘制图形时，都需要传递该图形的名称（当然也可以传递其他具有标记的参数），为识别后面不同的构造函数做准备                    bundle.putString("which", rect.getText().toString().trim());                    bundle.putString("x0", x_0);                    bundle.putString("y0", y_0);                    bundle.putString("x1", x_1);                    bundle.putString("y1", y_1);                    intent.putExtras(bundle);                    startActivity(intent); // 实现跳转                    break;                } else {
                       Toast.makeText(MainActivity.this, "请输入完整数据！", Toast.LENGTH_SHORT).show();                    break;                }            case R.id.circle:                if (!isEmpty(px) && !isEmpty(py) && !isEmpty(radius)) {
                       String p_x = px.getText().toString();                    String p_y = py.getText().toString();                    String p_radius = radius.getText().toString();                    Intent intent = new Intent(MainActivity.this, draw_RCL.class);                    Bundle bundle = new Bundle();                    bundle.putString("which", circle.getText().toString().trim());                    bundle.putString("px", p_x);                    bundle.putString("py", p_y);                    bundle.putString("radius", p_radius);                    intent.putExtras(bundle);                    startActivity(intent);                    break;                } else {
                       Toast.makeText(MainActivity.this, "请输入完整数据！", Toast.LENGTH_SHORT).show();                    break;                }            case R.id.line:                if (!isEmpty(lx1) && !isEmpty(ly1)                        && !isEmpty(lx2) && !isEmpty(ly2)) {
                       String lx_1 = lx1.getText().toString().trim();                    String lx_2 = lx2.getText().toString().trim();                    String ly_1 = ly1.getText().toString().trim();                    String ly_2 = ly2.getText().toString().trim();                    Intent intent = new Intent(MainActivity.this, draw_RCL.class);                    Bundle bundle = new Bundle();                    bundle.putString("which", line.getText().toString().trim());                    bundle.putString("lx1", lx_1);                    bundle.putString("ly1", ly_1);                    bundle.putString("lx2", lx_2);                    bundle.putString("ly2", ly_2);                    intent.putExtras(bundle);                    startActivity(intent);                    break;                } else {
                       Toast.makeText(MainActivity.this, "请输入完整数据！", Toast.LENGTH_SHORT).show();                    break;                }            default:                break;        }    }    // 判断文本框是否有数据？    public boolean isEmpty(TextView textView) {
           if (textView.getText().toString().equals(""))            return true;        else            return false;    }

draw_RCL.java文件（处理从上一个Activity传递过来的参数，并识别、调用对应构造函数，以实现绘制出满足要求的图形）

public class draw_RCL extends Activity {
       @Override    protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);                // 获取上一个界面的“图形”名称        Bundle bundle = this.getIntent().getExtras();        String draw_name = bundle.getString("which");//        FrameLayout f = findViewById(R.id.frame);        if (draw_name.equals("矩形")) {
   //            f.addView(new PaintRCL(draw_RCL.this, draw_name, x0, y0, x1, y1));            float x0 = Float.parseFloat(bundle.getString("x0"));            float y0 = Float.parseFloat(bundle.getString("y0"));            float x1 = Float.parseFloat(bundle.getString("x1"));            float y1 = Float.parseFloat(bundle.getString("y1"));            setContentView(new PaintRCL(this, draw_name, x0, y0, x1, y1)); // 矩形的构造函数        }        // 绘制圆形        if (draw_name.equals("圆形")) {
               float px = Float.parseFloat(bundle.getString("px"));            float py = Float.parseFloat(bundle.getString("py"));            float radius = Float.parseFloat(bundle.getString("radius"));//            f.addView(new PaintRCL(this, draw_name, px, py, radius));            setContentView(new PaintRCL(this, draw_name, px, py, radius));        }        // 绘制直线        if (draw_name.equals("直线")) {
   //            f.addView(new PaintRCL(draw_RCL.this, lx1, ly1, lx2, ly2));            float lx1 = Float.parseFloat(bundle.getString("lx1"));            float ly1 = Float.parseFloat(bundle.getString("ly1"));            float lx2 = Float.parseFloat(bundle.getString("lx2"));            float ly2 = Float.parseFloat(bundle.getString("ly2"));            setContentView(new PaintRCL(this, lx1, ly1, lx2, ly2));        }    }}

PaintRCL继承View，并重写Ondraw()方法

public class PaintRCL extends View {
       private float x0, y0, x1, y1;    private float px, py, radius;    private float lx1, lx2, ly1, ly2;    private String name = "";    // 矩形的构造方法    public PaintRCL(Context context, String name, float x0, float y0, float x1, float y1) {
           super(context);        this.name = name;        this.x0 = x0;        this.y0 = y0;        this.x1 = x1;        this.y1 = y1;    }    // 圆形的构造方法    public PaintRCL(Context context, String name, float px, float py, float radius) {
           super(context);        this.name = name;        this.px = px;        this.py = py;        this.radius = radius;    }    // 直线的构造方法    public PaintRCL(Context context, float lx1, float ly1, float lx2, float ly2) {
           super(context);        this.name = "直线";        this.lx1 = lx1;        this.ly1 = ly1;        this.lx2 = lx2;        this.ly2 = ly2;    }    protected void onDraw(Canvas canvas) {
           // 绘制矩形        if (name.equals("矩形")) {
               Paint paint = new Paint();            paint.setColor(Color.RED);            paint.setTextSize(40);            canvas.drawText("画矩形：", 10, 80, paint);            paint.setStrokeWidth(5);            paint.setStyle(Paint.Style.STROKE);            canvas.drawRect(x0, y0, x1, y1, paint);        }        // 绘制圆形        if (name.equals("圆形")) {
               Paint paint = new Paint();            paint.setColor(Color.GREEN);            paint.setTextSize(50);            paint.setStrokeWidth(2);            paint.setStyle(Paint.Style.STROKE);            canvas.drawText("画圆形：", 10, 80, paint);            canvas.drawCircle(px, py, radius, paint);//            canvas.drawCircle(800, 800, 100, paint);        }        // 绘制直线        if (name.equals("直线")) {
               Paint paint = new Paint();            paint.setColor(Color.BLUE);            paint.setStrokeWidth(5);            paint.setStyle(Paint.Style.STROKE);            Path path = new Path();            paint.setTextSize(50);            canvas.drawText("画直线：", 10, 80, paint);            path.moveTo(lx1, ly1); // 移动到该点，但不绘制路径//            path.lineTo(lx1, ly1);            path.lineTo(lx2, ly2); // 从起点一直绘制路径到该点位置            path.close();            canvas.drawPath(path, paint);        }        super.onDraw(canvas);    }}

写博文的经验较少，在书面表述上可能存在诸多问题，希望在以后的文章里能够有所提升。上述代码的完成，少不了参照CSDN平台上其他优秀大佬的经验分享，在这里也非常开心能够分享自己的一点点经验，像优秀的大佬看齐，乐于分享自己的所得。

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